The present invention relates to recording apparatuses for intermittently recording picture data of a monitor camera or the like at a constant interval and, more particularly, to time lapse recorders, which comprise a motion correcting circuit, typically MPEG2 (xe2x80x9cGeneric coding of moving pictures and associated audio information: videoxe2x80x9d, ISO/IEC IS 13818-2), provided in a picture coding part and an HDD (hard disc drive) or a VCR (Video Cassette Recorder) provided in a recording unit part.
Time lapse VCRs (video tape recorders) using VTRs are well known in the art as an apparatus for intermittently recording an extracted part of a picture signal from a camera at a constant interval.
With the recent development of digital signal processing techniques, time lapse recorders are also used, in which image signal is digitized and data compressed by using a still image coding system, typically JPEG (xe2x80x9cDigital Compression Coding of Continuous-Tone Still Imagesxe2x80x9d, ISO/IEC IS 10918-1) for recording of the compressed data in a recording medium, such as HDD or an optical disc.
The time lapse recorder currently in practical use, has a problem that in the case of an analog VTR it is difficult to record high quality picture signal.
In the digital system case, it is possible to obtain high quality picture signal recording owing to the use of a still picture cording system. However, for executing abnormality detection and automatically reducing the picture signal recording interval when the abnormality is detected, an exclusive abnormality detector is necessary, so that the apparatus is increased in scale, complicated and increased in cost.
The present invention was made in view of the above problem, and it has an object of providing a time lapse recorder, which uses a motion picture coding system having a motion compensating circuit typically MPEG2 and thus can detect abnormality without exclusive abnormality detector, and in which when the abnormality is detected the recording interval is adaptively changed or the recording picture quality is improved to permit accurate recording of the abnormal phenomenon.
According to an aspect of the present invention, there is provided a time lapse recorder comprising: a dividing means for dividing an input picture signal into signals corresponding to small area blocks each consisting of a plurality of pixels; a motion estimate means for retrieving motion vectors of blocks most similar to each other in picture frames of different times; a motion compensating means for obtaining a difference between a coding subject frame and a motion vector computation frame for each of the blocks on the basis of the motion vectors; an orthogonal transform means for executing orthogonal transform of the blocks; a quantizing means for quantizing transform coefficient values as the output of the orthogonal transform means; a code quantity control means for controlling picture quality and quantity of codes generated per frame in accordance with the complexity of the input picture; a variable length coding means for variable length coding quantized coefficient data outputted from the quantizing means; an abnormality detecting means for detecting abnormality of input picture; a recording interval control means for changing recording frame number at a constant interval in the normal state and in unit times in the abnormality detection state; and a recording means for recording the variable length coded data in a recording medium under control of the recording interval control means, wherein the abnormality detecting means computes the coding bit number of the variable length coding means for each frame, compares the difference of this coding bit number from the coding bit number of the immediately preceding frame having the same predicted structure and executes abnormal detection when the compared difference is above a predetermined threshold value.
According to another aspect of the present invention, there is provided a time lapse recorder comprising: a dividing means for dividing an input picture signal into signals corresponding to small area blocks each consisting of a plurality of pixels; a motion estimate means for retrieving motion vectors of blocks most similar to each other in picture frames of different times; a motion compensating means for obtaining a difference between a coding subject frame and a motion vector computation frame for each of the blocks on the basis of the motion vectors; an orthogonal transform means for executing orthogonal transform of the blocks; a quantizing means for quantizing transform coefficient values as the output of the orthogonal transform means; a code quantity control means for controlling picture quality and quantity of codes generated per frame in accordance with the complexity of the input picture; a variable length coding means for variable length coding quantized coefficient data outputted from the quantizing means; an abnormality detecting means for detecting abnormality of input picture; a recording interval control means for changing recording frame number at a constant interval in the normal state and in unit times in the abnormality detection state; and a recording means for recording the variable length coded data in a recording medium under control of the recording interval control means, wherein the abnormality detecting means computes statistical value of the distribution or amplitude values of the motion vectors for each frame, compares the statistical value of the motion vectors with a predetermined threshold value, and executes abnormality detection when the statistical value is above the threshold value.
The recording interval control means adaptively controls the recording frame number according to a multiple-valued output of the abnormality detecting means. When the output of the abnormality detecting means is abnormal, the recording interval control means controls the recording frame number such as to permit recording of all frames. The abnormality detecting means provides a multiple-valued output, and the recording interval control means decodes the value of the output of the abnormality detecting means, selects a recording time interval corresponding to the output value among a plurality of different recording times shorter than a recording time in a normal state and causes the recording means to record frames at the selected recording time interval. The code quantity control means executes code quantity control on the basis of the output of the abnormality detecting means such as to provide an improved recording picture quality when the abnormality is detected.
According to other aspect of the present invention, there is provided in an image processing apparatus of moving picture coding type for detecting motion vectors from an input picture, variable length coding a motion corrected signal, and recording the coded signal in recording means, a time lapse recorder comprising: means for comparing a unit time mean coding bit number of past frames and the coding bit number of the present frame and executing abnormality detection on the basis of the difference between the compared coding bit numbers; and means for controlling the number of frames recorded in the recording means such that the recording interval per unit time is reduced when the abnormality is detected.
According to still other aspect of the present invention, there is provided inn an image recording apparatus for detecting motion vectors from an input picture, generating an inter-frame difference value between the input picture and a predicted frame from the motion vectors, executing orthogonal transform of the inter-frame difference, quantizing coefficients obtained by the orthogonal transformation, coding the quantized coefficients and recording the quantized coefficients in a recording means, a time lapse recorder comprising: an abnormality detecting mean for comparing a unit time mean coding bit number of past frames and the coding bit number of the present frame and executing abnormality detection on the basis of the difference between the compared coding bit numbers; and a recording interval control means for controlling the number of frames recorded in the recording means such that the recording interval per unit time is reduced when the abnormality is detected.
According to further aspect of the present invention, there is provided in an image recording apparatus for detecting motion vectors from an input picture, generating an inter-frame difference value between the input picture and a predicted frame from the motion vectors, executing orthogonal transform of the inter-frame difference, quantizing coefficients obtained by the orthogonal transformation, coding the quantized coefficients and recording the quantized coefficients in a recording means, a time lapse recorder comprising: an abnormality detecting means including means for computing the unit time least mean coding bit number on the basis of the frame coding bit number of each frame, and means for comparing the coding bit number of the present frame and the least mean coding bit number and determines that the frame is abnormal when the difference is greater than a predetermined threshold value; and a recording interval control means for controlling the number of frames recorded in the recording means such that the recording interval per unit time is reduced when the abnormality is detected.
According to still further aspect of the present invention, there is provided in an image recording apparatus for detecting motion vectors from an input picture, generating an inter-frame difference value between the input picture and a predicted frame from the motion vectors, executing orthogonal transform of the inter-frame difference, quantizing coefficients obtained by the orthogonal transformation, coding the quantized coefficients and recording the quantized coefficients in a recording means, a time lapse recorder comprising: an abnormality detecting means including means for computing the unit time least mean coding bit number on the basis of the frame coding bit number of each frame, and means for comparing the coding bit number of the present frame and the least mean coding bit number and determines that the frame is abnormal when the difference is greater than a predetermined threshold value; and a recording interval control means for controlling the number of frames recorded in the recording means such that the recording interval per unit time is reduced when the abnormality is detected, wherein a plurality of threshold values are provided, and abnormality detection is executed by a multiple-valued state detection as a result of comparison between the difference and the plurality of threshold values.
The abnormality detecting means includes: means for selecting a frame having a predetermined predicted structure among input frames; means for receiving frame coding bit number of the selected frame and computing the unit time least mean coding bit number; and means for executing abnormality detection and providing an abnormality detection signal when the quotient of division of the mean coding bit number by the least mean coding bit number is greater than a predetermined threshold value and also when the quotient of division of the coding bit number of the selected present input frame by the unit time least mean coding bit number is greater than a predetermined threshold value. The frame coding bit number is inputted when P picture frames alone or P and B picture frames are inputted. The abnormality detecting means includes: means for analyzing the motion vector over one frame; and means for comparing the motion vector value distribution with a predetermined value, executing abnormality detection when it is larger than the predetermined value, and generating an abnormal detection signal. The abnormality detecting means includes: means for converting the motion vector amplitudes to corresponding scalar values; means for accumulating the scalar values for each frame; and means for comparing the accumulation value with a predetermined threshold value and outputting an abnormality detection signal when the accumulation value is greater than the threshold value. The recording interval control means normally executes a control for recording frames at a predetermined recording time interval in the recording means; and when the abnormality detecting means detects abnormality, the variable length coding means is controlled on the basis of the value of the output of the abnormality detecting means such that all frames are recorded continuously or at a recording time interval shorter than the recording time interval in the normal state. An abnormal detection signal is outputted when it is determined from a motion vector value and coordinate data of a base block of the motion vector that motion coordinates of the motion vector are in a predetermined monitoring area. When the abnormality detecting means detects abnormality, the code quantity control means controls the quantizing means and the variable length coding means for recording frames in the recording means at an increased coding rate and a reduced compression factor compared to the normal state.
Other objects and features will be clarified from the following description with reference to attached drawings.